Body fluid measuring apparatus with lancet and lancet holder used for the measuring apparatus

ABSTRACT

A body fluid measuring apparatus includes a main body ( 20 ) and a lancet holder ( 30 ) for attachment to the main body ( 20 ). The lancet holder ( 30 ) includes a lancet ( 31 ) which is movable for stabbing a skin (S) to draw body fluid, and a biosensor ( 36 ) for introducing the drawn body fluid to perform predetermined measurement. The biosensor ( 36 ) is moved in a predetermined direction by a sensor moving mechanism ( 40, 42 ).

TECHNICAL FIELD

[0001] The present invention relates to a body fluid measuring apparatusprovided with a lancet, which is capable of sampling and measuring bodyfluid by a single operation for checking a substance contained thereinsuch as the glucose concentration in blood (hereinafter referred to as“blood glucose level”). The present invention also relates to a lancetholder removably attached to such a body fluid measuring apparatus.

BACKGROUND ART

[0002] For diabetes treatment, the blood glucose level of a patient needbe maintained in a normal range. Thus, the management of the bloodglucose level by the patient himself or herself is important.Particularly, for keeping the blood glucose level in a normal range byinsulin injection, measurement of the blood glucose level by the patienthimself or herself is essential.

[0003] A portable blood glucose level measuring apparatus used for sucha purpose is already commercially available, an example of which isdisclosed in JP-A-4-357452. This blood glucose level measuring apparatusis used by inserting a disposable test piece provided with an enzymeelectrode into a main body. When the test piece is brought into contactwith blood as an analyte, a portion of the blood is introduced into areacting portion by capillary action, thereby generating an anodecurrent due to an enzyme reaction or an electrochemical reaction. In theapparatus, the anode current is converted to a blood glucose level,which is displayed.

[0004] In such a measuring apparatus as described above, the analyte,i.e. blood for contact with the test piece is generally sampled using aninstrument called lancet as disclosed in JP-A-9-266898 for example. Alancet is a tool used for making a small hole (or making a cut) on theskin of a fingertip, for example, of a patient. The blood drawn from thehole thus formed is brought into contact with a predetermined portion ofthe test piece. Thus, the self-measurement of the blood glucose levelcan be performed relatively easily.

[0005] However, the conventional self-measurement of the blood glucoselevel is inconvenient in that the lancet for sampling blood as ananalyte is separate from the measuring apparatus, so that the two toolsneed be carried. Moreover, it is necessary to separately perform thesteps of injuring the skin with the lancet and of bringing the blooddrawn from the cut into contact with the test piece. Therefore, there isstill room for improvement in terms of the convenience of use.Particularly, in bringing the blood into contact with the test piece, anecessary amount of blood need be brought into contact with apredetermined portion of the test piece. Therefore, in the case wherethis step is performed by an untrained or week-sighted patient or whereblood is drawn from an earlobe which cannot be observed by the patienthimself or herself, it is not easy to bring the blood drawn from the cutinto contact with the test piece quickly and properly.

[0006] Further, the test piece is designed to suck blood from a hole atthe tip end of the test piece into the biosensor provided in thereacting portion by capillary action. Therefore, 3 to 5 μl of blood needbe brought into contact with the test piece to ensure that a necessaryamount of blood reaches the reacting portion. If the amount of blood isinsufficient or if a sufficient amount of blood is not depositedappropriately on a small area surrounding the tip hole of the testpiece, the apparatus may suffer erroneous measurements. In particular,such a case is more likely to occur with respect to patients such asinfants and the elderly who tend to suffer insufficient drawing of bloodfrom a cut.

[0007] To solve the above-described problems, JP-A-10-28683 proposes ablood glucose level measuring apparatus provided with a lancet. Withthis apparatus, just by operating the lancet built in the apparatus toinjure the skin, the blood drawn from the skin can be measured by abiosensor also built in the apparatus. However, the apparatus disclosedin this gazette still has room for improvement in terms of convenience,because, in use, the lancet needle and the biosensor need beindividually set at predetermined positions in the apparatus.

[0008] For improving the convenience in use, the inventors of thepresent invention have proposed, in JP-A-10-166894, a lancet holderwhich integrates a lancet and a biosensor. According to this apparatus,the patient's action needed for measurement is simplified, therebyenhancing the convenience in use. Further, the reliability ofmeasurement is enhanced while decreasing the amount of analyte necessaryfor measurement. However, the reliability of measurement with a smallamount of analyte of not more than 1.0 μl has not yet been satisfactory.

DISCLOSURE OF THE INVENTION

[0009] It is therefore an object of the present invention to provide abody fluid measuring apparatus provided with a lancet, which is capableof realizing high measurement reliability even with a small amount ofanalyte without deteriorating the convenience.

[0010] Another object of the present invention is to provide a lancetholder for use in such a body fluid measuring apparatus.

[0011] A body fluid measuring apparatus according to a first aspect ofthe present invention includes a main body and a lancet holder forattachment to the main body. The lancet holder includes a lancet movablefor stabbing skin to draw body fluid, and a biosensor for introducingthe body fluid drawn to perform predetermined measurement. The biosensoris moved in a predetermined direction by sensor moving mechanism.

[0012] The lancet holder may be provided as a disposable article ofconsumption. For measurement, the user attaches the lancet holder to themain body. While holding the body fluid measuring apparatus so that thetip end of the lancet holder is pressed against the skin, the lancet ismoved back and forth by operating a lancet operating mechanism forexample. Such a movement of the lancet makes a cut on the skin, fromwhich body fluid (e.g. blood) is drawn. By keeping the holding state,the blood drawn is introduced into the biosensor for predeterminedmeasurement. According to the present invention, the sensor movingmechanism moves the biosensor so that the biosensor can locate moreclose to the blood drawn. As a result, even a small amount of blood of1.0 μl for example can be duly introduced into the reacting portion ofthe biosensor, which considerably enhances the reliability of themeasurement.

[0013] Preferably, the biosensor is shaped like a plate and internallyformed with a body fluid path having an inlet end. The biosensor isformed with an operative electrode and a counterpart electrode facingthe body fluid path at a position spaced from the inlet end. Since thebiosensor is shaped like a plate as a whole, the body fluid path formedtherein is small in volume, which is suitable for the measurement of asmall amount of analyte. Further, in the case where the operativeelectrode and the counterpart electrode are formed on the upper surfaceof the plate-shaped biosensor, conduction is easily established betweenthese electrodes and terminals of the main body.

[0014] Preferably, the body fluid measuring apparatus further comprisesbody fluid detecting means for detecting the drawn body fluid. Thesensor moving mechanism moves the biosensor in the predetermineddirection in response to a detection signal generated by the body fluiddetecting means. In the case where the body fluid detecting means isprovided, when the body fluid is not drawn, the biosensor is preventedfrom unnecessarily advancing. This is advantageous for avoiding ameasurement failure.

[0015] According to one embodiment of the present invention, the bodyfluid detecting means comprises a pair of conductance measuringelectrodes facing the body fluid path at the inlet end of the biosensor.The body fluid is detected by sensing conduction established between theconductance measuring electrodes due to the body fluid. Since theconductance measuring electrodes can be formed similarly to theoperative electrode and the counterpart electrode and at the same timeas forming such electrodes, the manufacturing cost can be reduced.Further, such a structure is convenient for establishing electricalconnection between the conductance measuring electrodes and terminals ofthe main body.

[0016] According to another embodiment of the present invention, thebody fluid detecting means is non-contact detection means for detectingexistence of the body fluid without contacting the body fluid drawn.With this structure, when a sufficient amount of body fluid is notdrawn, the biosensor is not contaminated. Therefore, the biosensortogether with the lancet holder can be reused so that the wasting can beprevented. The non-contact detection means comprises a light source(e.g. a light emitting diode) for emitting light toward the skin, and alight receiving element (e.g. a photodiode) for receiving reflectedlight from the drawn body fluid.

[0017] Preferably, the biosensor comprises a base plate having an uppersurface on which the operative electrode and the counterpart electrodeare formed, a pair of spacers spaced from each other and disposed on thebase plate, and a cover plate laminated on the spacers to bridge thespacers. The body fluid path is defined between the spacers.

[0018] Preferably, the body fluid path is formed with a reactive reagentlayer.

[0019] Preferably, the sensor moving mechanism comprises an eccentriccam driven by a motor for rotation, and the eccentric cam pushes an edgeof the biosensor.

[0020] Preferably, the main body includes a plurality of terminals forslidably contacting a plurality of electrodes formed on an upper surfaceof the biosensor, an electronic circuit connected to the plurality ofterminals, a lancet operation mechanism for moving the lancet forstabbing, and a display for displaying a measurement result. It ispreferable that each of the terminals preferably comprises an elasticconnector pin.

[0021] Preferably, the biosensor is held inclined so that one edge iscloser to the skin than an opposite edge, and the biosensor is movablealong an inclined movement path. In this case, it is preferable that thesensor moving mechanism acts on the opposite edge of the biosensor.

[0022] The biosensor includes a first electrode facing the body fluidpath at the inlet end, and a second electrode facing the body fluid pathat an end opposite to the inlet end. The filling of the body fluid pathwith the body fluid is detected by measuring conductance between thefirst electrode and the second electrode. In this case, for decreasingthe number of electrodes, it is preferable that the second electrode isone of the operative electrode and the counterpart electrode.

[0023] A lancet holder according to the second aspect of the presentinvention comprises a lancet which is movable for stabbing skin to drawbody fluid, and a biosensor for introducing the body fluid drawn toperform predetermined measurement. The biosensor is supported formovement in a predetermined direction.

[0024] Other features and advantages of the present invention willbecome clearer from the detailed description given below with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is an overall view illustrating a body fluid measuringapparatus according to the present invention.

[0026]FIG. 2 is a sectional view taken along lines II-II in FIG. 5,illustrating a lancet holder in which a lancet and a biosensor areretreated.

[0027]FIG. 3 is a sectional view similar to FIG. 2, illustrating alancet which is advanced and a biosensor which is retreated.

[0028]FIG. 4 is an enlarged sectional view illustrating a lancet whichis retreated and a biosensor which is advanced.

[0029]FIG. 5 is a bottom view of the lancet holder.

[0030]FIG. 6 is a schematic perspective view showing the internalstructure of the main body.

[0031]FIG. 7 is a plan view of the biosensor.

[0032]FIG. 8 is a sectional view taken along lines VIII-VIII of FIG. 7.

[0033]FIG. 9 is an exploded perspective view of the biosensor.

[0034] FIGS. 10-12 illustrate the operation of the biosensor.

[0035]FIG. 13 is a flowchart illustrating an example of process forcontrolling the sampling and measuring of the body fluid.

[0036]FIG. 14 is a sectional view showing a principal portion accordingto another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0037] Preferred embodiments of the present invention will be describedbelow with reference to the accompanying drawings.

[0038] As shown in FIGS. 1 through 3, a body fluid measuring apparatus10 according to a preferred embodiment of the present invention is usedwith a lancet holder 30 fitted to a cylindrical tip end 21 of a mainbody 20. The main body 20 has an outer surface provided with a display22 and may incorporate a small speaker (not shown) for vocally reportingthe measurement result to the user. Further, the main body 20incorporates a lancet operation mechanism for advancing a lancet 31 heldby the lancet holder 30, a sensor moving mechanism for advancing abiosensor 36, and an electronic circuit 33 (See FIG. 6) such as amicrocomputer.

[0039] The lancet operation mechanism for advancing the lancet 31comprises a pushing rod 23 projecting from the rear end of the main body21 for manual pushing by the user, and a connection rod 32 connected tothe pushing rod 23 for movement following the pushing rod 23. The sensormoving mechanism for advancing the biosensor 36 comprises a motor 40 andan eccentric cam 42 fixed to a rotational shaft 41 of the motor 40.

[0040]FIGS. 2 and 5 illustrate an example of lancet holder 30. Theillustrated lancet holder 30 has a cap-like configuration comprising acylindrical wall 34 and a bottom wall 35 partially closing the end ofthe cylindrical wall 34. The cylindrical wall 34 and the bottom wall 35are formed by molding a resin. The cylindrical wall 34 has an innerdiameter corresponding to the outer diameter of the cylindrical tip end21 of the main body 20 for easy attachment and detachment relative tothe cylindrical tip end 21. The cylindrical wall 35 has a lower end 34 awhich, in use, comes into contact with the user's skin S.

[0041] The cap-shaped lancet holder 30 incorporates the lancet 31 andthe biosensor 36. The bottom wall 35 includes a thin-walled portion 35 afrom which a cylindrical housing 35 b stands. The cylindrical housing 35b has an upper end closed with a lid 35 c. The lid 35 c is formed with acentral hole 35 d.

[0042] The lancet 31 includes a guide shaft 31 a slidably fitted intothe central hole 35 d, a flange 31 b formed at the lower end of theguide shaft 31, and a stabbing needle 31 c projecting from the flange 31b. The guide shaft 31 a and the flange 31 b are formed by molding aresin and integral with each other. The stabbing needle 31 c, which isformed of a metal, is inserted integrally together with the resinmolding. The lancet 31 is normally biased toward a retreated position(the position at which the flange 31 b contacts the lid 35 c) shown inFIG. 2 by an elastic member 37 arranged in the housing 35 b in contactwith the flange portion 31 b. At the retreated position, the upper endof the guide shaft 31 a projects inwardly from the lid 35 c, whereas thestabbing needle 31 c retreats from the lower end 34 a of the cylindricalwall 34. The thin-walled portion 35 a of the lancet holder 30 is formedwith a round hole 35 f. The stabbing needle 31 c advances and retreatsthrough the round hole 35 f.

[0043] In the illustrated embodiment, the elastic member 37 is acompression coiled spring formed of a metal or a resin. Alternatively,the elastic member may be formed of a resilient material such as foamedurethane. In the case where the elastic member 37 is made of foamedurethane, the stabbing needle 31 c is embedded in the foamed urethanewhen the lancet 31 is at the retreated position so that the stabbingneedle is less likely to be contaminated. Further, the elastic member 37may be a leaf spring integrally formed on the guide member 31 a formedof a resin.

[0044] The plate-like biosensor 36 is slidably supported, as inclined,by the bottom wall 35 of the lancet holder 30 adjacent to the lancet 31.As shown in FIGS. 7 and 9, the biosensor 36 has an elongated rectangularconfiguration. The biosensor 36 includes an insulating base plate 361, apair of plate-shaped spacers 362, 362′ laminated on the insulating baseplate 361, and a plate-shaped cover 363 further laminated on theplate-shaped spacers 362, 362′. The insulating base plate 361 has anupper surface formed with a pair of conductance measuring electrodes 36a, 36 a′, an operative electrode 36 c and a counterpart electrode 36 d.The insulating base plate 361, the two plate-shaped spacers 362, 362′and the plate-shaped cover 363 define a body fluid path 36 b (See FIG.8). Part of the conductance measuring electrodes 36 a, 36 a′, part ofthe operative electrode 36 c and part of the counterpart electrode 36 dface the body fluid path 36 b. The body fluid path 36 b accommodates areaction reagent portion 36 e.

[0045] The biosensor 36 may be manufactured as follows. First, as shownin FIG. 9, an elongated rectangular base plate 361 is prepared from aninsulating resin sheet having a thickness of 0.2 mm for example.

[0046] Subsequently, conductance measuring electrodes 36 a, 36 a′, anoperative electrode 36 c, and a counterpart electrode 36 d are formed onan upper surface of the base plate 361 as film strips extendinglongitudinally of the base plate 36 a by screen-printing a graphite ink.The conductance measuring electrodes 36 a, 36 a′, the operativeelectrode 36 c, and the counterpart electrode 36 d may be alternativelyprovided by forming a film of noble metal such as gold, palladium orplatinum by vapor deposition to entirely cover the upper surface of thebase plate 361 and then etching the metal film into a predeterminedpattern.

[0047] Subsequently, a pair of rectangular spacer plates 362, 362′ aredisposed on the base plate 361 while keeping a spacing therefrom whichis slightly larger than the spacing between the two conductancemeasuring electrodes 36 a and 36 a′. Each spacer plate 362, 362′ may bea resin plate having a thickness of 0.2 mm for example and fixed to thebase plate 361 with a double-sided adhesive tape for example. The bodyfluid path 36 b may be 1.0 mm in width, 3 mm in length and 0.2 mm indepth (which is equal to the thickness of the spacer plates 362, 362′)for example.

[0048] Then, as clearly shown in FIG. 8, a reactive reagent layer 36 eis formed in the body fluid path 36 b by the dispensing method forexample. In the case where the biosensor 36 is used for measuring theblood glucose level, the reactive reagent layer 36 e contains glucoseoxidase which is an oxidization enzyme, and potassium ferricyanide as amediator.

[0049] Subsequently, as shown in FIG. 9, a rectangular cover plate 363is attached to cover the spacer plates 362, 362′, thereby completing thebiosensor 36. As a result, the body fluid path 36 b is upwardly closedby the cover plate 363. However, the body fluid path 36 b is open at theopposite ends thereof for allowing body fluid (blood) to enter the bodyfluid path 36 b due to capillary action for reaction with the reactivereagent layer 36 e. The body fluid path 36 b of the above dimensions hasa volume of 0.6 μl, which is found by 1.0 mm×3 mm×0.2 mm. Bysubtracting, from this value, 0.2 μl which is the approximate solidvolume of the reactive reagent layer 36 e, it is found that the bodyliquid flow path 36 b has an extremely small net volume of about 0.4 μl.

[0050] As clearly shown in FIG. 2, the plate-like biosensor 36 issupported, as inclined, by the bottom wall 35 of the lancet holder 30 sothat the stabbing needle 31 c is located adjacent to the conductancemeasuring electrodes 36 a, 36 a′. The biosensor 36 is so inclined thatthe side formed with the conductance measuring electrodes 36 a, 36 a′ iscloser to the user's skin than the counterpart electrode 36 d.

[0051] The biosensor 36 is slidably movable to approach the stabbingneedle 31 c by the sensor moving mechanism 40 which will be describedlater. As shown in FIGS. 4 and 5, the bottom wall 35 of the lancetholder 30 is formed with a round hole 35 e for fitting to the lower endof the rotational shaft 41 of the motor 41. Thus, when the lancet holder30 is attached to the main body 20, the rotational center of theeccentric cam 42 is precisely determined. Further, the bottom wall 35 ofthe lancet holder 30 is formed with a pair of arcuate openings 36 f (SeeFIG. 5) sandwiching the biosensor-supporting region. By the provision ofthe openings 36 f, a negative pressure generating mechanism for examplemay be provided in the main body for exerting a negative pressure to theskin while holding the cylindrical wall 34 of the lancet holder 30 incontact with the skin S.

[0052] As shown in FIGS. 4 through 7, the cylindrical tip end 21 of themain body 20 is provided with four pin connectors 25 a, 25 b, 25 c, 25 deach having a tip end projecting from the cylindrical end 21 into thelancet holder 30. The pin connectors 25 a-25 d individually andelastically contact the exposed portions (i.e. portions which are notcovered with the cover 363) of the electrodes 36 a, 36 a′ 36 c 36 d ofthe biosensor 36. The pin connectors 25 a-25 d are connected to theelectronic circuit 33 (See FIG. 6). The electronic circuit 33, which maycomprise a microcomputer, has a function of determining the value of ananalyte such as the blood glucose level from the current generated dueto enzyme reaction or electrochemical reaction in the biosensor 36 byutilizing the calibration curve, a function of displaying the determinedvalue at the display 22 of the main body 20, and a function ofcontrolling the sensor moving mechanism 40 for moving the biosensor 36.

[0053] In the illustrated embodiment, the eccentric cam 42 driven by themotor 41 for rotation includes a bevel surface. When the lancet holder30 is attached to the body 20, the bevel surface comes into contact withan edge of the biosensor 36 (the edge which is opposite to the edgeformed with the conductance measuring electrodes 36 a, 36 a′). Thedegree of eccentricity of the cam 41 is set in accordance with thestroke for moving the biosensor 36 (e.g. 0.1-0.5 mm) . The rotationalinitial position of the cam 42 is detected by a rotary encoder 43.

[0054] In use, the body fluid measuring apparatus 10 having the abovestructure operates in the manner described below.

[0055] The lancet holder 30 is supplied as a disposable article ofconsumption. In using the body fluid measuring apparatus 10, the userattaches the lancet holder 30 to the cylindrical portion 21 of the mainbody 20 (See FIG. 1). Since the lancet holder 30 is shaped like a cap inthe illustrated embodiment, the attaching operation can be performedeasily. As shown in FIG. 2, by the attachment of the lancet holder 30,the connector pins 25 a, 25 b, 25 c, 25 d on the side of the main body20 automatically come into contact with the electrodes 36 a, 36 a′, 36c, 36 d of the biosensor 36.

[0056] Subsequently, with the lower end 34 a of the cylindrical wall 34of the lancet holder 30 pressed against an appropriate portion of theuser's skin such as a fingertip or an earlobe, the pushing portion 23 ispushed down. As a result, the pushing rod 32 within the main body 20pushes the guide shaft 31 a of the lancet 31 to advance the lancet 31against the elastic force of the elastic member 37 until the pushing rod32 comes into contact with the lid 35 c of the lancet holder 30. At thistime, the stabbing needle 31 c of the lancet 31 passes adjacent to theinlet of the body fluid path 36 b of the biosensor 36 to project fromthe lower end 34 a of the cylindrical wall 34 by a predetermined length(the state shown in FIG. 3). When the pushing portion 23 is relieved,the pushing rod 32 is restored to its original position by the elasticforce of the spring. Further, due to the elastic force of the elasticmember 37, the lancet 31 also returns to its retreated position wherethe stabbing needle 31 c retreats from the lower end 34 a of thecylindrical wall 34 (the state shown in FIG. 2).

[0057] The projection of the stabbing needle 31 c makes an appropriatecut on the skin S to draw blood B, which is introduced to the inlet ofthe body fluid path 36 b of the biosensor 36 by capillary action. At themoment when the blood enters the inlet of the body fluid path 36 b ofthe biosensor 36, current flows across the paired conductance measuringelectrodes 36 a, 36 a′ so that a signal is generated due to the changeof the conductance. In response to the signal, the motor 41 drives thebiosensor 36 through the eccentric cam 42 for forward movement. Thisprompts the blood to be sucked into the body fluid path 36 b.

[0058] As described above, since the net volume of the body fluid path36 b in the biosensor 36 is extremely small and the biosensor 36 isadvanced toward the blood, the body fluid path 36 b is reliably filledwith a small amount of blood. Therefore, blood can be introduced intothe body fluid path 36 b in an amount just necessary for the measurementsimply by conducting the above operation while keeping the lancet holder30 pressed against the skin S for a predetermined period of time. Thus,it is not necessary to visually monitor the amount of blood drawn. Asdescribed before, a negative pressure generating mechanism such as asuction cylinder may be provided in the main body to apply a negativepressure to the skin S through the openings 36 f of the lancet holder30. In such a case, a cut is formed on the skin in a congestive state bythe stabbing needle 31 c so that a required amount of blood is morereliably drawn.

[0059] Next, with reference to the operational figures of FIGS. 10-12and the flowchart of FIG. 13, the operation of the apparatus will bedescribed in more detail by showing an example of the controllingoperation by the electronic circuit 33.

[0060] First, when the switch of the main body is turned on, theposition of the eccentric cam 42 is initialized (S01). At this time, asshown in FIGS. 2 and 10, the biosensor 36 is located at the mostretreated position. The initialized state is detected by the rotaryencoder 43.

[0061] In this state, the user conducts the bleeding operation byholding the apparatus with the lancet holder 30 pressed against the skinS and operating the lancet 31 in the above-described manner (FIG. 3). Asdescribed before, since the inlet of the body fluid path 36 b of thebiosensor is arranged close to the lancet 31 in advance, the blood Bdrawn from the skin contacts the inlet of the body fluid path 36 b. Thisstate is detected due to a change in the resistance between the twoconductance measuring electrodes 36 a, 36 a′. Specifically, whether thebleeding has occurred or not is determined by measuring the resistancebetween the pin connectors 25 a and 25 b corresponding to theconductance measuring electrodes 36 a, 36 a′ (S02).

[0062] If bleeding is not detected within a predetermined period of time(S02: NO, S03: YES), a failure warning is given vocally or by displaying(S04) to urge the user to retry.

[0063] If the bleeding is detected (S02: YES), the bleeding is reportedvocally for example (S05), and the eccentric cam 42 is driven to advancethe biosensor 36 (S06). Thus, as shown in FIGS. 4 and 11, the biosensor36 is moved so that the inlet of the body fluid path 36 b projects intothe drawn blood. As a result, the blood is reliably introduced into thebody fluid path 36 b due to capillary action. As described before, thebiosensor 36 is so inclined that the inlet of the body fluid path 36 bis closer to the skin whereas the opposite side is farther from theskin. This arrangement prevents the reverse surface of the advancedbiosensor 36 from contacting the skin, thereby preventing the blood fromreaching the reverse surface of the sensor. Thus, the waste of blood canbe prevented.

[0064] Subsequently, it is determined whether the body fluid path 36 bis filled with the blood (S07). As shown in FIG. 11, this may beperformed, for example, by measuring the resistance between one of theconductance measuring electrodes 36 a, 36 a′ and the counterpartelectrode 36 d. This is because, when the body fluid path 36 b is filledwith blood, a current flows across these electrodes.

[0065] If the body fluid path 36 b is not filled with the blood within apredetermined period of time (S07: NO, S08: YES), a failure warning isgiven vocally or by displaying (S09) to urge the user to retry.

[0066] If it is determined that the body fluid path 36 b is filled withblood (S07: YES), a notice is given vocally or by displaying that theapparatus may be removed from the skin S for example (S10). Thus, themeasurement starts in S11 (See FIG. 12), and the result is displayed(S12) to terminate the process.

[0067] When the reactive reagent layer 36 e is dissolved in the blood inthe body fluid path 36 b in the biosensor 36, an enzyme reaction starts,as represented by the formula (1) given below. As a result, potassiumferricyanide contained in the reactive reagent layer 36 e is reduced tocumulatively produce potassium ferrocyanide which is a reduced-typeelectron carrier .

[0068] The amount of potassium ferrocyanide is proportional to theconcentration of the substrate, i.e., the glucose concentration in theblood. The reduced-type electron carrier produced in a predeterminedtime is oxidized by the electrochemical reaction represented by thefollowing formula (2).

Fe(CN)₆ ⁴⁻→Fe(CN)₆ ³⁻ +e ⁻  (2)

[0069] The electronic circuit 33 in the main body 20 of the measuringapparatus 10 performs calculation to determine the glucose level (bloodglucose level) based on the detected operative electrode current anddisplays the result on the LCD display 22 provided at the main body 20.

[0070] In this way, with the body fluid measuring apparatus 10 accordingto the present invention, it is possible to perform body fluidmeasurement such as blood glucose level measurement just by performingthe preparation step of placing the lancet holder 30 at a predeterminedportion of the main body 20 and the bleeding step of advancing thelancet 31 while keeping the tip end of the lancet holder 30 pressedagainst a fingertip or earlobe of the patient. Therefore, it is notnecessary to separately perform, after the bleeding step, a measuringstep by using other measuring instrument than the lancet. Further, sincethe biosensor 36 is advanced after the bleeding, the measurement can bereliably performed even with a small amount of blood.

[0071] As is clear from the above description, the gist of the presentinvention lies in that the body fluid measuring apparatus 10 comprises adisposable lancet holder 30 which integrates both a biosensor 36 and alancet 31 and which is attached to the main body 20, whereby the lancet31 causes bleeding of body fluid (blood) toward which the biosensor 36is advanced for causing the sensor 36 to be internally filled with thebleeding fluid. Therefore, all the modifications within such a spiritare included in the scope of the present invention. Although some of thepossibilities of modification have already been described, othermodifications are also possible, as described below.

[0072] In the above embodiment, the biosensor 36 progresses from theretreated position to the advanced position in one step. However, thebiosensor 36 may progress in two steps. Specifically, the biosensor 36is initially held at the retreated position which is spaced from thelancet 31 by a certain distance. After the stabbing operation by thelancet 31, the biosensor 36 may be advanced to a detection position fordetecting the blood drawn. Then, after the detection of the blood, thebiosensor 36 may be further advanced to the most advanced position.

[0073] In the above embodiment, blood is detected by measuring theconductance (resistance) between the conductance measuring electrodes 36a, 36 a′ at the inlet of the body fluid path 36 b of the biosensor 36.However, the blood may be detected by non-contact detection means. Forexample, as shown in FIG. 14, the main body 20 may be provided withoptical detection means including a light emitting element 51 foremitting light toward the skin S and a light receiving element 52 forreceiving light reflected by the skin S. Thus, whether or not blood isproperly drawn may be determined by measuring the amount of light ofparticular wavelength range (e.g. red light) received by the lightreceiving element 52. In this case, the light emitting element 52 may bea light emitting diode (LED) or a laser generator. As another example ofoptical detection means, the blood image on the skin may be captured bya small CCD camera and the size of a region having a particular colormay be measured and computed to detect the bleeding state. Further,instead of the optical detection means, detection means utilizingultrasonic waves may be employed. In the case where such non-contactdetection means is used, the bleeding can be confirmed withoutcontaminating the biosensor, thereby avoiding wasting of the biosensor.

[0074] According to the present invention, however, the drawing of theblood need not necessarily be confirmed. Therefore, on the assumptionthat the pushing of the lancet 31 inevitably causes bleeding, thebiosensor 36 may be advanced when a predetermined period of time haspassed after the pushing of the lancet 31.

[0075] In the illustrated embodiment, the lancet operation mechanismincludes a pushing portion 23 for manual operation and a pushing rod 32movable together with the pushing portion 23 so that the lancet 31normally biased toward the retreating direction by the elastic member 37(compression coil spring) is pushed forward (See FIGS. 2 and 3 ).Alternatively, though not illustrated, a lancet 31 may constantly belatched at a retreated position as elastically biased in the advancingdirection so that the lancet 31 hits the skin by a resilient elasticforce when the latch is manually released.

[0076] Further, as the sensor moving mechanism for moving the biosensor36, use may be made of a solenoid, a piezo-electric element,shape-memory alloy, or a spring instead of the motor-driven eccentriccam 42 of the above embodiment.

[0077] In the illustrated embodiment, the elastic pin connectors 25 a-25d provided in the main body 20 are electrically connected to theelectrodes of the biosensor 36 when the lancet holder 30 is attached tothe main body 20. Instead of this, pin connectors, which are normallyretreated within the main body 20, may project from the main body 20 forcontact with the electrodes of the biosensor in response to theattachment of the lancet holder 30 to the main body 20.

[0078] In the illustrated embodiment, the body fluid measuring apparatus10 is described as an apparatus for measuring the blood glucose level.However, the measurement is not limited to the blood glucose level.Further, the specific design of the lancet holder 30 and the biosensor36 may be varied in various ways. For example, the biosensor 36 may beprovided with a reagent pad which exhibits color reaction uponcontacting an analyte (body fluid), and the degree of the color reactionis optically measured. In this case, the detection of the body fluidbleeding from the skin is preferably performed optically. After theexistence of the body fluid is detected, the biosensor is moved to aposition for contacting the body fluid. After the body fluid is dulyintroduced to the reagent pad, the degree of reflection of the lightemitted from the light source to the reacting portion is opticallymeasured.

1. A body fluid measuring apparatus comprising: a main body; and a lancet holder for attachment to the main body; wherein the lancet holder includes a lancet movable for stabbing a skin to draw body fluid, and a biosensor for introducing the drawn body fluid to perform predetermined measurement; and wherein a sensor moving mechanism is further provided for moving the biosensor in a predetermined direction.
 2. The body fluid measuring apparatus according to claim 1, wherein the biosensor is shaped like a plate and internally formed with a body fluid path having an inlet end, the biosensor being formed with an operative electrode and a counterpart electrode facing the body fluid path at a position spaced from the inlet end.
 3. The body fluid measuring apparatus according to claim 2, further comprising body fluid detecting means for detecting the drawn body fluid, the sensor moving mechanism moving the biosensor in the predetermined direction in response to a detection signal generated by the body fluid detecting means.
 4. The body fluid measuring apparatus according to claim 3, wherein the body fluid detecting means comprises a pair of conductance measuring electrodes facing the body fluid path at the inlet end of the biosensor, the body fluid being detected by sensing conduction established between the conductance measuring electrodes due to the body fluid.
 5. The body fluid measuring apparatus according to claim 2, wherein the body fluid detecting means is non-contact detection means for detecting existence of the body fluid without contacting the drawn body fluid.
 6. The body fluid measuring apparatus according to claim 5, wherein the non-contact detection means comprises a light source for emitting light toward the skin, and a light receiving element for receiving reflected light from the drawn body fluid.
 7. The body fluid measuring apparatus according to claim 2, wherein the biosensor comprises a base plate having an upper surface on which the operative electrode and the counterpart electrode are formed, a pair of spacers spaced from each other and disposed on the base plate, and a cover plate laminated on the spacers to bridge the spacers, the body fluid path being defined between the spacers.
 8. The body fluid measuring apparatus according to claim 2, wherein the body fluid path is formed with a reactive reagent layer.
 9. The body fluid measuring apparatus according to claim 1, wherein the sensor moving mechanism comprises an eccentric cam driven by a motor for rotation, the eccentric cam pushing an edge of the biosensor.
 10. The body fluid measuring apparatus according to claim 1, wherein the main body includes a plurality of terminals for slidably contacting a plurality of electrodes formed on an upper surface of the biosensor, an electronic circuit connected to the plurality of terminals, a lancet operation mechanism for moving the lancet for stabbing, and a display for displaying a measurement result.
 11. The body fluid measuring apparatus according to claim 10, wherein each of the terminals comprises an elastic connector pin.
 12. The body fluid measuring apparatus according to claim 1, wherein the biosensor is held inclined so that one edge is closer to the skin than an opposite edge, the biosensor being movable along an inclined movement path.
 13. The body fluid measuring apparatus according to claim 12, wherein the sensor moving mechanism acts on the opposite edge of the biosensor.
 14. The body fluid measuring apparatus according to claim 2, wherein the biosensor includes a first electrode facing the body fluid path at the inlet end, and a second electrode facing the body fluid path at an end opposite to the inlet end, filling of the body fluid path with the body fluid being detected by measuring conductance between the first electrode and the second electrode.
 15. The body fluid measuring apparatus according to claim 14, wherein the second electrode is one of the operative electrode and the counterpart electrode.
 16. A lancet holder comprising: a lancet which is movable for stabbing a skin to draw body fluid, and a biosensor for introducing the body fluid drawn to perform predetermined measurement; wherein the biosensor is supported for movement in a predetermined direction. 